In this work,an old scanning electron microscope(SEM)is refurbished to enhance its image processing capability.How to digitally sample and process an analog image is also presented.An NI PCI-6259 multiple input/output...In this work,an old scanning electron microscope(SEM)is refurbished to enhance its image processing capability.How to digitally sample and process an analog image is also presented.An NI PCI-6259 multiple input/output data acquisition(DAQ)board is used to acquire signals originally being sent to an analog display,and then convert the signals into a digital image.Two output channels are used for raster scan of the horizontal and verticle axes of the image buffer,while one input channel is used to read the brightness signals at various coordinate points.Synchronous method is used to maximize the DAQ speed.Finally,the digitally buffered images are read out to display and saved in a hard drive.The hardware and software designs of this work are explained in great detail,which can serve as a very good example for fast synchronous DAQ,advanced virtual instrument design and structural driver programming with LabVIEW.展开更多
The aim of this work is to simulate thermal deformation of tool system and investigate the influence of cutting parameters on it in single-point diamond turning(SPDT) of aluminum alloy. The experiments with various cu...The aim of this work is to simulate thermal deformation of tool system and investigate the influence of cutting parameters on it in single-point diamond turning(SPDT) of aluminum alloy. The experiments with various cutting parameters were conducted. Cutting temperature was measured by FLIR A315 infrared thermal imager. Tool wear was measured by scanning electron microscope(SEM). The numerical model of heat flux considering tool wear generated in cutting zone was established. Then two-step finite element method(FEM) simulations matching the experimental conditions were carried out to simulate the thermal deformation. In addition, the tests of deformation of tool system were performed to verify previous simulation results. And then the influence of cutting parameters on thermal deformation was investigated. The results show that the temperature and thermal deformation from simulations agree well with the results from experiments in the same conditions. The maximum thermal deformation of tool reaches to 7 μm. The average flank wear width and cutting speed are the dominant factors affecting thermal deformation, and the effective way to decrease the thermal deformation of tool is to control the tool wear and the cutting speed.展开更多
Hydroxyapatite coatings were directly prepared on anodized titanium by electro-deposition method in a modified simulated body fluid.The configuration,structure and bioactivity of the coating were investigated with sca...Hydroxyapatite coatings were directly prepared on anodized titanium by electro-deposition method in a modified simulated body fluid.The configuration,structure and bioactivity of the coating were investigated with scanning electron microscopy(SEM),X-ray diffraction analyzer(XRD)and Fourier transform infrared spectros-copy(FTIR)techniques.The results demonstrated that pure and homogeneous hydroxyapatite coating can be obtained without any post-treatment.The prepared coating showed good bioactivity in simulated body fluid(SBF).The time required for a fully covered dense hydroxyapatite coatings was 4 days immersion in SBF.展开更多
This study utilizes ANSYS to establish FEM's model of metamorphic core complex,and used thermal-structure analysis to simulate metamorphic core complex's temperature field and stress field.The metamorphic core...This study utilizes ANSYS to establish FEM's model of metamorphic core complex,and used thermal-structure analysis to simulate metamorphic core complex's temperature field and stress field.The metamorphic core complex formation mechanism is discussed.The simulation results show that the temperature field change appearing as the earth surface's temperature is the lowest,and the temperature of metamorphic core complex's nucleus is the highest.The temperature field is higher along with depth increase,and the stress field change appearing as the biggest stress occurs in the nucleus.The next stress field occurs at the top of the cover.展开更多
MC （Monte Carlo） simulation code, JA-IPU is used to study radiation damage of SiC irradiated to spallation neutron and AmBe neutron spectra. The code is based on the major physical processes of radiation damage on i...MC （Monte Carlo） simulation code, JA-IPU is used to study radiation damage of SiC irradiated to spallation neutron and AmBe neutron spectra. The code is based on the major physical processes of radiation damage on incorporation of atomic collision cascade and limited to 10 MeV neutron energy. A phenomenological relation for radiation swelling is also derived. Based on the calculation of swelling, DPA （displacement per atom）, defect production efficiency and effective threshold energy, Efff from the data of MC simulation, SiC is inferred to be a highly radiation resistant material when compared with Nb and Ni metals which are used in composition of several reactor steels. Experimental results of hill-hock density measured using AFM （atomic force microscopy）, also confirm radiation resistant behavior of SiC.展开更多
Super hydrophobic copper wafer was prepared by means of solution immersion and surface self-assembly methods. Different immersion conditions were explored for the best hydrophobic surface. Scanning electron microscopy...Super hydrophobic copper wafer was prepared by means of solution immersion and surface self-assembly methods. Different immersion conditions were explored for the best hydrophobic surface. Scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and water contact angle measurements were used to investigate the morphologies, microstructures, chemical compositions and hydrophobicity of the produced films on copper substrates, respectively. Results show that the super hydrophobic surface is composed of micro structure of Cu 7 S 4 . The films present a high water contact angle larger than 150°, a low sliding angle less than 3°, good abrasion resistance and storage stability. The molecular dynamics simulation confirms that N-dodecyl mercaptan molecules link up with Cu 7 S 4 admirably, compared with Cu, which contributes to the stable super hydrophobic surface.展开更多
Porous and dense TiNi alloys were successfully fabricated by powder metallurgy(P/M) method, and to further improve their surface biocompatibility, surface modification techniques including grind using silicon-carbide(...Porous and dense TiNi alloys were successfully fabricated by powder metallurgy(P/M) method, and to further improve their surface biocompatibility, surface modification techniques including grind using silicon-carbide(SiC) paper, acid etching and alkali treatment were employed to produce either irregularly rough surface or micro-porous surface roughness. X-ray diffractometry(XRD), scanning electron microscopy(SEM) and energy dispersive X-ray spectroscopy(EDX) attached to SEM were used to characterize surface structure and the Ca-P coatings. Effects of the above surface treatments on the surface morphology, apatite forming ability were systematically investigated. Results indicate that all the above surface treatments increase the apatite forming ability of TiNi alloys in varying degrees when soaked in simulated body fluid(SBF). More apatite coatings formed on TiNi samples sintered at 1050℃ and 1100℃ due to their high porosity and pure TiNi phase that is beneficial to heterogeneous nucleation. Furthermore, more uniform apatite was fabricated on the sample sintered from the mixture of Ni and Ti powders.展开更多
In the last decades, surface drag reduction has been re-emphasized because of its practical values in engineering applications,including vehicles, aircrafts, ships, and fuel pipelines. The bionic study of drag reducti...In the last decades, surface drag reduction has been re-emphasized because of its practical values in engineering applications,including vehicles, aircrafts, ships, and fuel pipelines. The bionic study of drag reduction has been attracting scholars' attentions. Here, it was determined that the delicate microstructures on the scales of the fish Ctenopharyngodon idellus exhibit remarkable drag-reduction effect. In addition, the underlying drag-reduction mechanism was carefully investigated. First,exceptional morphologies and structures of the scales were observed and measured using a scanning electron microscope and3-dimensional(3D) microscope. Then, based on the acquired data, optimized 3D models were created. Next, the mechanism of the water-trapping effect of these structures was analyzed through numerical simulations and theoretical calculations. It was determined that there are many microcrescent units with certain distributions on its surface. In fact, these crescents are effective in generating the "water-trapping" effect and forming a fluid-lubrication film, thus reducing the skin friction drag effectively.Contrasting to a smooth surface, the dynamics finite-element analysis indicated that the maximum drag-reduction rate of a bionic surface is 3.014% at 0.66 m/s flow rate. This study can be used as a reference for an in-depth analysis on the bionic drag reduction of boats, underwater vehicles, and so forth.展开更多
The plastic deformation and the ultrahigh strength of metals at the nanoscale have been predicted to be controlled by surface dislocation nucleation. In situ quantitative tensile tests on individual 〈111〉 single cry...The plastic deformation and the ultrahigh strength of metals at the nanoscale have been predicted to be controlled by surface dislocation nucleation. In situ quantitative tensile tests on individual 〈111〉 single crystalline ultrathin gold nanowires have been performed and significant load drops observed in stress-strain curves suggest the occurrence of such dislocation nucleation. High-resolution transmission electron microscopy （HRTEM） imaging and molecular dynamics simulations demonstrated that plastic deformation was indeed initiated and dominated by surface dislocation nucleation, mediating ultrahigh yield and fracture strength in sub-lO-nm gold nanowires.展开更多
文摘In this work,an old scanning electron microscope(SEM)is refurbished to enhance its image processing capability.How to digitally sample and process an analog image is also presented.An NI PCI-6259 multiple input/output data acquisition(DAQ)board is used to acquire signals originally being sent to an analog display,and then convert the signals into a digital image.Two output channels are used for raster scan of the horizontal and verticle axes of the image buffer,while one input channel is used to read the brightness signals at various coordinate points.Synchronous method is used to maximize the DAQ speed.Finally,the digitally buffered images are read out to display and saved in a hard drive.The hardware and software designs of this work are explained in great detail,which can serve as a very good example for fast synchronous DAQ,advanced virtual instrument design and structural driver programming with LabVIEW.
基金Project(51175122)supported by the National Natural Science Foundation of China
文摘The aim of this work is to simulate thermal deformation of tool system and investigate the influence of cutting parameters on it in single-point diamond turning(SPDT) of aluminum alloy. The experiments with various cutting parameters were conducted. Cutting temperature was measured by FLIR A315 infrared thermal imager. Tool wear was measured by scanning electron microscope(SEM). The numerical model of heat flux considering tool wear generated in cutting zone was established. Then two-step finite element method(FEM) simulations matching the experimental conditions were carried out to simulate the thermal deformation. In addition, the tests of deformation of tool system were performed to verify previous simulation results. And then the influence of cutting parameters on thermal deformation was investigated. The results show that the temperature and thermal deformation from simulations agree well with the results from experiments in the same conditions. The maximum thermal deformation of tool reaches to 7 μm. The average flank wear width and cutting speed are the dominant factors affecting thermal deformation, and the effective way to decrease the thermal deformation of tool is to control the tool wear and the cutting speed.
基金Supported by the Young Scholars Fund of Beijing University of Chemical Technology(QN0713)
文摘Hydroxyapatite coatings were directly prepared on anodized titanium by electro-deposition method in a modified simulated body fluid.The configuration,structure and bioactivity of the coating were investigated with scanning electron microscopy(SEM),X-ray diffraction analyzer(XRD)and Fourier transform infrared spectros-copy(FTIR)techniques.The results demonstrated that pure and homogeneous hydroxyapatite coating can be obtained without any post-treatment.The prepared coating showed good bioactivity in simulated body fluid(SBF).The time required for a fully covered dense hydroxyapatite coatings was 4 days immersion in SBF.
文摘This study utilizes ANSYS to establish FEM's model of metamorphic core complex,and used thermal-structure analysis to simulate metamorphic core complex's temperature field and stress field.The metamorphic core complex formation mechanism is discussed.The simulation results show that the temperature field change appearing as the earth surface's temperature is the lowest,and the temperature of metamorphic core complex's nucleus is the highest.The temperature field is higher along with depth increase,and the stress field change appearing as the biggest stress occurs in the nucleus.The next stress field occurs at the top of the cover.
文摘MC （Monte Carlo） simulation code, JA-IPU is used to study radiation damage of SiC irradiated to spallation neutron and AmBe neutron spectra. The code is based on the major physical processes of radiation damage on incorporation of atomic collision cascade and limited to 10 MeV neutron energy. A phenomenological relation for radiation swelling is also derived. Based on the calculation of swelling, DPA （displacement per atom）, defect production efficiency and effective threshold energy, Efff from the data of MC simulation, SiC is inferred to be a highly radiation resistant material when compared with Nb and Ni metals which are used in composition of several reactor steels. Experimental results of hill-hock density measured using AFM （atomic force microscopy）, also confirm radiation resistant behavior of SiC.
基金Supported by the Beijing Youth Fellowship Program and the Fundamental Research Funds for the Central Universities(2011YXL056)
文摘Super hydrophobic copper wafer was prepared by means of solution immersion and surface self-assembly methods. Different immersion conditions were explored for the best hydrophobic surface. Scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and water contact angle measurements were used to investigate the morphologies, microstructures, chemical compositions and hydrophobicity of the produced films on copper substrates, respectively. Results show that the super hydrophobic surface is composed of micro structure of Cu 7 S 4 . The films present a high water contact angle larger than 150°, a low sliding angle less than 3°, good abrasion resistance and storage stability. The molecular dynamics simulation confirms that N-dodecyl mercaptan molecules link up with Cu 7 S 4 admirably, compared with Cu, which contributes to the stable super hydrophobic surface.
基金Project(51274247) supported by the National Natural Science Foundation of ChinaProject(2014zzts177) support by the Fundamental Research Funds for the Central Universities,China
文摘Porous and dense TiNi alloys were successfully fabricated by powder metallurgy(P/M) method, and to further improve their surface biocompatibility, surface modification techniques including grind using silicon-carbide(SiC) paper, acid etching and alkali treatment were employed to produce either irregularly rough surface or micro-porous surface roughness. X-ray diffractometry(XRD), scanning electron microscopy(SEM) and energy dispersive X-ray spectroscopy(EDX) attached to SEM were used to characterize surface structure and the Ca-P coatings. Effects of the above surface treatments on the surface morphology, apatite forming ability were systematically investigated. Results indicate that all the above surface treatments increase the apatite forming ability of TiNi alloys in varying degrees when soaked in simulated body fluid(SBF). More apatite coatings formed on TiNi samples sintered at 1050℃ and 1100℃ due to their high porosity and pure TiNi phase that is beneficial to heterogeneous nucleation. Furthermore, more uniform apatite was fabricated on the sample sintered from the mixture of Ni and Ti powders.
基金supported by the National Natural Science Foundation of China(Grant Nos.51305282,51505183&51325501)Program for Excellent Talents of Liaoning Provincial Committee of Education(Grant No.LJQ2014071)
文摘In the last decades, surface drag reduction has been re-emphasized because of its practical values in engineering applications,including vehicles, aircrafts, ships, and fuel pipelines. The bionic study of drag reduction has been attracting scholars' attentions. Here, it was determined that the delicate microstructures on the scales of the fish Ctenopharyngodon idellus exhibit remarkable drag-reduction effect. In addition, the underlying drag-reduction mechanism was carefully investigated. First,exceptional morphologies and structures of the scales were observed and measured using a scanning electron microscope and3-dimensional(3D) microscope. Then, based on the acquired data, optimized 3D models were created. Next, the mechanism of the water-trapping effect of these structures was analyzed through numerical simulations and theoretical calculations. It was determined that there are many microcrescent units with certain distributions on its surface. In fact, these crescents are effective in generating the "water-trapping" effect and forming a fluid-lubrication film, thus reducing the skin friction drag effectively.Contrasting to a smooth surface, the dynamics finite-element analysis indicated that the maximum drag-reduction rate of a bionic surface is 3.014% at 0.66 m/s flow rate. This study can be used as a reference for an in-depth analysis on the bionic drag reduction of boats, underwater vehicles, and so forth.
文摘The plastic deformation and the ultrahigh strength of metals at the nanoscale have been predicted to be controlled by surface dislocation nucleation. In situ quantitative tensile tests on individual 〈111〉 single crystalline ultrathin gold nanowires have been performed and significant load drops observed in stress-strain curves suggest the occurrence of such dislocation nucleation. High-resolution transmission electron microscopy （HRTEM） imaging and molecular dynamics simulations demonstrated that plastic deformation was indeed initiated and dominated by surface dislocation nucleation, mediating ultrahigh yield and fracture strength in sub-lO-nm gold nanowires.
